Tylosaurus rex: The “T. rex of the Sea” – 13-Meter Mosasaur with Bone-Crushing Jaws Emerges as Ancient Ocean’s New Apex Terror

Paleontologists have crowned a new king of the Cretaceous seas: Tylosaurus rex, a colossal mosasaur stretching up to 43 feet (13 meters) long with serrated, bone-shredding teeth and one of the most powerful bites in marine reptile history. Described May 21, 2026, in the Bulletin of the American Museum of Natural History, this “king of the tylosaurs” rewrites our understanding of Late Cretaceous ocean predators.

Led by Amelia Zietlow of the American Museum of Natural History, researchers re-examined more than a dozen fossils previously lumped under Tylosaurus proriger. The holotype specimen, on display at Dallas’s Perot Museum, comes from 80-million-year-old rocks of the Western Interior Seaway that once flooded Texas. At roughly the length of two city buses, T. rex was a top-tier hunter capable of ambushing plesiosaurs, sharks, and even other mosasaurs.

Its standout feature? Distinctive serrated teeth—rare among mosasaurs—paired with a robust skull and mᴀssive jaw muscles that delivered devastating crushing power. These adaptations made it a versatile apex predator in a warm, shallow inland sea teeming with life. The find elevates Tylosaurus as one of the largest and most formidable mosasaurs ever known, rivaling the terrestrial Tyrannosaurus rex in fearsome reputation.

This discovery underscores how much remains hidden in museum collections and forces a rethink of mosasaur evolution: giant size and specialized denтιтion appeared earlier and more diversely than previously thought. With the specimen now drawing crowds and casts heading to other insтιтutions, Tylosaurus rex proves the ancient oceans were ruled by monsters every bit as spectacular as their land-dwelling cousins.